This invention relates to spinal implant insertion tools for insertion of intervertebral fusion implants.
Of interest is commonly owned copending application Ser. No. 09/328,242 entitled Ramp Shaped Intervertebral Implant filed Jun. 8, 1999 in the name of John W. Boyle incorporated by reference herein.
Surgical procedures for fusing adjacent vertebrae to treat various pathologies are well known. Implants for such procedures take a wide variety of shapes, forms and materials from bone to titanium inert materials, rigid and elastic, circular cylindrical, wedge shapes, cages with or without openings to accept bone fusion promoting material. The implant disclosed in the aforementioned application is preferred. The implants are dimensioned and shaped to provide a predetermined disc space between the fused adjacent vertebra.
Published PCT international applications WO 99/09914 and WO 00/24327 disclose C-shaped implants and tools related to surgery and to insertion of the implants.
U.S. Pat. No. 4,878,915 to Brantigan illustrates a spinal implant and insertion tool. The implant is circular cylindrical and has a threaded bore and two opposing radial slots at one end for receiving an insertion tool threaded stud and prongs. A sleeve with the prongs is slidably attached to the shaft of the insertion tool. The sleeve is advanced on the shaft of the stem of the tool to bottom the prongs on the sleeve in the slots in the implant.
U.S. Pat. No. 4,736,738 to Lipovsek et al. discloses an instrument kit and procedure for performing posterior lumbar interbody fusion.
U.S. Pat. No. 4,904,261 to Dove et al. illustrates an inert C-shaped spinal fusion implant.
U.S. Pat. No. 5,192,327 to Brantigan discloses a prosthetic implant for vertebrae. One or more plug implants are attached to an insertion tool by internally threaded hole in the plug. In the alternative, the plug may have a pair of side-by-side holes for receiving the tine end of a tool having a pair of tines. The tines engage the holes in the implant and thus require special holes for the insertion tool tines. In the alternative, the plug may have a threaded hole for receiving a threaded insertion tool.
U.S. Pat. No. 5,522,899 to Michelson discloses and insertion tool with a threaded portion for engaging a threaded opening in the implant. The engaging end of the insertion driver tool has a slightly convex surface to complement the surface of the implant and an extrusion for fitting within a depressed portion in the implant. The tool also has a restriction member for restricting the depth of penetration of the driver.
U.S. Pat. No. 5,653,762 (""762) discloses an applicator for an implant which is screwed into the implant. When the applicator is fully screwed in place, the implant is then inserted by the applicator.
U.S. Pat. No. 5,716,416 to Lin discloses insertion of an elastic intervertebral implant.
U.S. Pat. No. 5,720,751 discloses spinal insertion tools including a tool with opposing implant engaging portions and including a pusher assembly. In one embodiment the implant engaging portions are fixed and in other embodiments the insertion portion is formed of two arms secured in scissor-like fashion. A pusher may include a threaded stem for attachment to the handle for advancement of the pusher bar toward and away from the implant by rotation of the threaded stem.
U.S. Pat. No. 5,741,253 to Michelson, discloses a threaded self tapping spinal implant and insertion instrumentation. The implant is tubular and cylindrical and is inserted in an opening in the spine formed by a drill inserted in a sleeve.
U.S. Pat. No. 5,443,514 to Steffee discloses an instrument for holding and inserting a spinal implant and which includes an intermediate portion, a handle and a clamp portion. The implant is wedge shaped with two opposing flat parallel surfaces and two inclined surfaces which converge toward one end. The flat surfaces have recesses which receive the clamp of the instrument. The clamp comprises clamp halves with outwardly tapering surfaces and extensions which are received in the recesses. The extensions engage the flat bottom surfaces of the recesses. The clamp halves are drawn into mating inclined surfaces of the intermediate portion to force the clamp extensions against the implant recess bottom surfaces to compress the extensions against the implant. The insertion tool rotates the implant after it is inserted between adjacent vertebrae.
U.S. Pat. No. 5,782,830 to Farris discloses an implant insertion tool somewhat similar to the Steffee disclosure in that a pair of articulating jaws clamp an implant therebetween
U.S. Pat. No. 6,033,438 discloses an open intervertebral spacer and tools and methods for insertion. The spacers have open mouth chambers. One spacer is an open-mouth plug from the diaphysis of a long bone forming a dowel disclosed as generally cylindrical. The chamber of the spacer has a truncated arm forming a channel for use with and for receiving an insertion tool. The channel permits osteogenic material to be packed within the chamber after implantation.
U.S. Pat. Nos. 5,885,299, 5,885,300, 5,910,141, 6,004,326, 6,033,405, 6,042,582 and 6,063,088 illustrate still other insertion tools for a spinal implant.
None of the above patents or applications address or recognize a problem with insertion of a C-shaped ramp as disclosed in the aforementioned copending application Ser. No. 09/328,242. In this ramp, a side of the implant is C-shaped and open. During surgery, it is desired to fill the C-shaped opening with fusion promoting material such as bone chips to facilitate bone fusion of the adjacent vertebrae in a posterior insertion procedure. Also during this procedure, two side by side spaced implants may be inserted into the evacuated disc space between two adjacent vertebra. One or two small openings may be made on the posterior side of the spinal region. Two implants are then inserted through the one opening on one side of the spinal cord or through a respective different one of two openings on opposing sides of the spinal cord. There is thus little room for the insertion tool The ""438 patent attempts to address this problem.
Tools with articulated clamps need to have the clamps opened after the implant is inserted. Such opening requires the jaws to separate which may be detrimental to the surrounding tissue and also requires additional space in the disk space for such articulation. Some insertion tools attach to the implant solely by threads such as in the ""762 patent. However, if the implant rotates during insertion, this may cause a problem.
As known, it is desired to fill the space around the implants with fusion promoting material such as bone chips and so on. However to fill the open space after the implants are inserted may be difficult. Even in those procedures where two openings are provided on each side of the spinal cord for separate implants, a problem of filling the space with bone growth promoting material to promote fusion may be difficult due to the small space available. In Pat. No. ""438 an insertion tool is used with a truncated implant in which one arm is truncated relative to the other. The patent describes the fusion material as being added after insertion of the implant.
In respect to tools such as disclosed in the ""438 patent, the present invention recognizes that the surgeon needs to align the implant with the disc space and such alignment with the disclosed tool may be difficult as the implant and tool interface are relatively small and may be difficult to align to the disc space.
The present invention is a recognition of these problems and is directed to provide a solution.
A spinal implant insertion tool according to the present invention is for inserting the implant into the disc space between two adjacent vertebra, the disc space having a given orientation relative to the spine, the implant having opposing first and second end surfaces and first and second opposing sides extending generally in a longitudinal direction between and toward the end surfaces, at least a third side having a flat surface located between the end surfaces, and a threaded bore in the first end surface. The tool comprises an elongated shank having a central longitudinal axis, the shank having an implant receiving surface at one end transverse to the axis for abutting the implant first end surface. An extension member extends from the one end in the axial direction and offset from the axis arranged to abut the third side surface of the implant. A threaded member extends axially from the implant receiving surface for engagement with the threaded bore, the extension member being arranged relative to the implant to preclude rotation of the implant relative to the shank about the axis. A guide member is secured to the shank and has a predetermined orientation relative to the extension member for providing visual alignment of the extension member relative to the disc space orientation during insertion of the implant.
In one aspect, the extension member has a flat surface for abutting the flat third side of the implant.
In a further aspect, the guide member comprises a rod extending from the shank at the predetermined orientation relative to the plane of the flat surface.
In a further aspect, the implant is C-shaped with a concave recess in the third side wall and forming fourth and fifth sides, the extension member having a length sufficient to overlap the concave recess of the received implant including the fourth and fifth sides and cooperating with the implant concave surface for entrapping bone growth material in the recess therebetween.
In a further aspect, a shaft is secured to the threaded member and rotatably secured to the shank for rotating the threaded member independently of the shank and extension member to secure the implant to the shank.
In a further aspect, a knob is secured to the shaft distal the threaded member for assisting in the manually gripping of the shaft and rotating the threaded member.
In a still further aspect, the shank comprises a tubular member with a hollow core, the shaft being rotatably mounted in the core.
Preferably, a bore is in the knob for receiving a rod transversely the shaft length to assist in the manual rotation of the knob.
In a further aspect, the extension member flat surface defines a plane, the shank including a transverse threaded bore spaced from the extension member for receiving and securing the guide member normal to the axis and normal to the plane.
Preferably the shank includes an annular collar extending about the shank periphery, the threaded bore being formed in the collar.
In a further aspect, the shank is tubular with a hollow core further including a shaft fixedly attached to the threaded member rotatably secured to the shank in the core, a collar surrounding the shank adjacent to the shank end distal the extension, the shank forming a sleeve between the shank end distal the extension and collar, and an end cap member secured to the sleeve for enclosing the core and shaft.
In a further aspect, the implant comprises a fourth side wall coextensive with the third side wall, the extension member for abutting the fourth side wall and for fully overlying said concave recess.